The present invention relates to a sealed rolling bearing having a bearing space between inner and outer rings and which is sealed with contact seals.
As rolling bearings used in environments where dust flies and water splashes, sealed rolling bearings are typically used. The sealed rolling bearings have their bearing space sealed with contact seals to prevent entry of dust and water into the bearing space. The contact seals include lips that are in sliding contact with the inner or outer ring to seal the bearing space.
Some of such sealed rolling bearings include two such contact seals each provided on one side of the bearing space (as disclosed in JP utility model publication 7-10555A (FIG. 1); Reference 1). Other sealed rolling bearings include, besides such two contact seals, non-contact shields each provided outside of one of the two contact seals (as disclosed in JP utility model publication 8-3710A (FIGS. 1 and 2); Reference 2, and JP patent publication 2001-50288A (FIGS. 1 and 3 to 10); Reference 3). Each shield of the bearing disclosed in Reference 2 comprises two separate members, one mounted on the outer ring and the other mounted on the inner ring. A labyrinth space is formed between the two separate members. The bearing disclosed in Reference 3 has a labyrinth space formed between each shield (cover) and the inner contact seal. References 2 and 3 also disclose embodiments in which the contact seals include lips that are in contact with the respective shields.
Rolling bearings used to support center shafts of vehicle propeller shafts and joint shafts of drive shafts are provided under vehicle floors. Thus, such rolling bearings tend to be splashed with muddy water and hit by flying stones.
For such a rolling bearing, if the rolling bearing disclosed in Reference 1 were to be used, splashed muddy water would adhere to the lips of the contact seals or the sliding contact surfaces of the inner or outer ring, causing the lips and/or the sliding contact surfaces to become worn by mud contained in such muddy water. This extremely lowers the sealability of the bearing space.
In the sealed rolling bearings disclosed in References 2 and 3, the shields prevent muddy water from adhering directly to the lips of the contact seals and the sliding contact surfaces. However, since there exists a gap between each shield and the inner or outer ring, muddy water tends to infiltrate through the labyrinth gaps into gaps between the shields and the contact seals. The water content of muddy water in the gaps between the shields and the contact seals will evaporate, so that the concentration of mud in the muddy water will increase. When such muddy water, of which the concentration of mud has increased, adheres to the lips of the contact seals and the sliding contact surfaces, these portions will become worn. This lowers sealability of the bearing space.
An object of the present invention is to provide a sealed rolling bearing which can keep high sealability even if used in environments where muddy water splashes.